Novel Diastereomeric Thymidine Cyclic 3',5'-threo-Phosphoramidates.

Abstract Novel diastereomeric thymidine cyclic 3′,5′-threo-phosphoramidates were prepared by the treatment of 5-azido derivative of threo-thymidine with triphenyl phosphite as well as by the treatment of the corresponding amino derivative with phenyl phosphodichloridate. Phosphoramidation of the regioisomeric 3′-and 5′-azido derivatives of erythro-thymidine by means of triphenyl phosphite afforded the open-chain 3′-and 5′-phosphoramidates. The reaction which afforded the cyclic products was assumed to proceed via the cyclic tetraoxazaphosphorane intermediates.